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Neural Plasticity
Volume 2016, Article ID 8742725, 11 pages
Research Article

Background Noise Contributes to Organic Solvent Induced Brain Dysfunction

1Cell & Molecular Pathology Laboratory, Communication Sciences and Disorders, Northern Arizona University, Flagstaff, AZ, USA
2Loma Linda VA Medical Center, Loma Linda, CA, USA
3Head & Neck Surgery, Loma Linda University Medical Center, Loma Linda, CA, USA
4Naval Medical Research Unit and Molecular Bioeffects, Wright-Patterson Air Force Base, Dayton, OH, USA

Received 19 August 2015; Accepted 22 December 2015

Academic Editor: Preston E. Garraghty

Copyright © 2016 O’neil W. Guthrie et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Occupational exposure to complex blends of organic solvents is believed to alter brain functions among workers. However, work environments that contain organic solvents are also polluted with background noise which raises the issue of whether or not the noise contributed to brain alterations. The purpose of the current study was to determine whether or not repeated exposure to low intensity noise with and without exposure to a complex blend of organic solvents would alter brain activity. Female Fischer344 rats served as subjects in these experiments. Asynchronous volume conductance between the midbrain and cortex was evaluated with a slow vertex recording technique. Subtoxic solvent exposure, by itself, had no statistically significant effects. However, background noise significantly suppressed brain activity and this suppression was exacerbated with solvent exposure. Furthermore, combined exposure produced significantly slow neurotransmission. These abnormal neurophysiologic findings occurred in the absence of hearing loss and detectable damage to sensory cells. The observations from the current experiment raise concern for all occupations where workers are repeatedly exposed to background noise or noise combined with organic solvents. Noise levels and solvent concentrations that are currently considered safe may not actually be safe and existing safety regulations have failed to recognize the neurotoxic potential of combined exposures.